1. Field of Invention
This invention relates to an apparatus used to transport, convey, or move various objects, such as packages, from one location to another; and, more particularly, to coatings or liners for the surfaces on which the objects are transported, conveyed or moved; and a method of applying such coating or liner to such surface.
2. Description of the Prior Art
In the package shipping industry, the package is processed for trans-shipment using a stationary chute where the package is caused to be moved along by an external force, such as gravity. The chute may come in various sizes and shapes, such as an inclined slide with a stopper wall or horizontal plane at the bottom thereof, a spiral channel going from one floor to another, a circular angled flat surface, etc. The term "chute" is defined elsewhere herein. Almost every package shipping and processing station has one or more chutes which are used in the processing of the packages.
The most troublesome problem in the package shipping industry has been the continual pile-up or build-up of the packages in the chutes. The packages inevitably tend to stick and/or bridge, and cause a back-up of the packages and a shut down of the conveying line. This problem may be caused most often by defective design of the chutes as well as by such factors as humidity (e.g. the packages are wet) and the condition and/or composition of the packages (e.g. "shrink wrapped" plastic coating). There is poor compatibility between the chute surface and the packages. But, due to cost and other considerations, there has been very little change in the structural design of the chutes. Thus, in the prior art, the problem of package build-up, bridging, sticking, back-up, and the like, has been approached in an ad hoc manner as to solutions for such problem. Some of these approaches are as follows, none of which are satisfactory.
The most obvious solution and which has been the most expensive has been for the operator to stop the transporting line, and then go to the chute location where there is bridging, etc, and using a pole or other ad hoc tool, knock the packages around until the back-up problem is solved. Unfortunately, many of the problems occur in hard to reach places. Thus, the human operator is often injured while trying to solve the problem. This increases considerably the Workman's Compensation rate, injury to the worker, and conveying line down time. Also, recent tightening of OSHA rules makes this solution outdated. In other words, this ad hoc solution is no longer feasible.
Also, when the packages are "wet" or "shrink wrapped", the transport surface of the chute was sprayed or painted with graphite paint or paraffin wax partially diluted with water. However, this solution was not satisfactory because of the costs involved and because of the contamination caused to other packages and other parts of the conveying system, such as to moving conveyor belts which would become coated with the wax and/or graphite and require frequent and costly replacement. Also, this solution is really no solution since the wax and/or graphite would be effective at most for only a day or so because most of the coating would tend to stick to the package and be taken away thereby. In this type of solution, we can also include use of oils and other similar material, which also have the same problem.
Another solution attempted in the prior art was covering the transporting surface with a sheet of UHMW (ultra high molecular weight) polyethylene. Although the polyethylene layer appears to be "slick", in point of fact, it is inherently non-stack in effect. The material tends to abrade in a manner similar to a sheet of plywood which may sliver and itself thereby cause the packages to bridge and stick. Once abraded, the UHMW polyethylene layer's coefficient of friction and surface energy will begin to have an adverse effect on movement of the package placed on its surface. Also, disadvantageously, the process of applying this UHMW layer is time consuming because it must be cut, bevelled, drilled, and countersunk with screws. The cost of installation is thus almost prohibitive. Accordingly, this solution is not satisfactory.
A further solution was recently suggested, but was found to have too many disadvantages to be economically feasible. This was to make the chutes of molded fiber glass with a high build epoxy coating on the conveying surfaces. It was discovered that such chutes factured easily, were difficult to repair, were of brittle material, and had inadequate release properties. Thus, rather than solve the problem of build up, this type of chute caused almost the same problem of build-up and accordingly, the problem was not solved satisfactorily.
Thus, the prior art had not yet satisfactorily resolved the problem of package buildup, bridging, sticking, etc., in chutes.